an external od can also be finish machined with a boring head as long as there isn't anything in the design to hinder it . Boring heads are available with 3/4 shank , so fitting a 440 with one won't be a problem .
The 440's like any of the tormachs are capable machines , but , they aren't as tight as industrial machines . Your may find yourself struggling to uphold some of your tight tolerances . At the same time someone with no experience can struggle with a top of the line machine if they don't know tricks on how to make things work . If you can learn to make it work then it'll work .
I think that as a designer it is a good exercise in understanding design vs actual machining and how to make the 2 jive for better efficiency and bottom line costs . I'm not referring to you or be offensive by any means , but I've worked with designers who really made our lives difficult when it came to making parts , tight tolerances where none is needed , features that just won't jive etc . It's good to have an understanding from both points of view and how to compromise if and when needed .
I wish I could give examples of how my 440's hold up to sizes and tolerances , except 95% of my machining is surfacing . The surfaces finish from the mills are fantastic and the parts mesh together well . My purposely undersized alignment pin holes are always spot on position-wise . I finish ream/chase the holes off the machine out of habit . I run to many machines at once and I know occasions will come up where I'd be too consumed mentally and pop in the wrong reamer and fudge a part , finishing off the machine prevents losing an hour or so
They are good little machines which I'm confident will handle anything I throw at them . You won't find anything better within the size or price range